The quantity of the liquid product dispensed and the quality of the dispersed spray are important parameters which can have a substantial impact on the performance of a liquid product applied via an atomized spray. This is particularly true when a relatively viscous or solids laden liquid product is being utilized to form a thin, uniform coating on a surface, and the total quantity of liquid product applied and quality of the dispersed spray directly impact the thickness and uniformity of the product coating.
Aerosol spray type dispensers have been utilized to atomize relatively viscous liquids, however, recently there has been a trend away from aerosol-type dispensing systems for environmental reasons. Thus, the use of a propellant, regardless of the type, makes an aerosol container less desirable than hand pump type spray dispensers.
Many manually actuated hand pump type spray dispensers have also been utilized to atomize liquids. However, when dispensing relatively viscous products such as cooking oil or vegetable oil based pan coatings, these devices have generally resorted to a dual stream impingement type nozzle. There are some problems and disadvantages to the impingement type nozzle when used to dispense such products. These impingement type nozzles are more difficult to manufacture because the individual passages of the nozzle must be accurately aligned with the precision required for repetitively producing discharge streams that intersect or collide at a particular point in order for atomization of the liquid product to occur. Additionally, the small size of the multiple exit orifices required in an impingement nozzle, for increasing the velocity of the liquid, are prone to clog when dispensing a solids laden liquid product.
When using a manually actuated pump sprayer to dispense a relatively viscous liquid product certain challenges exist, especially when attempting to dispense the liquid in a dispersed spray. A dispersed spray as used herein, for example, is a dispensed liquid which breaks up and forms droplets or disintegrates into an atomized spray. The dispersed spray can contain droplets of liquid that are finely dispersed, such as an atomized spray, or even more coarsely dispersed representing larger droplets of liquid. Relatively viscous liquids typically have a tendency to resist break-up rather than easily being dispensed in a dispersed spray. As a general proposition, the less finely dispersed the atomized spray, the more difficult it is to achieve a comparatively thin and uniform coating of product on a surface.
Also problematic when dispensed using a manually actuated pump sprayer are solids laden liquid products, that is, liquids having a substantial amount of solid materials suspended in them. Typically, liquid products that contain solid particles have a tendency to clog and obstruct the small passageways of spray nozzles. Thus, dispensing of liquid products in a dispersed spray is especially problematic when the relatively viscous liquid also contains a substantial amount of solid materials.
One particularly troublesome product to dispense with a manually operated pump sprayer because of its relatively viscous and generally solids laden nature, is a vegetable oil based liquid product used in food preparation, such as, for example, pan coatings and liquid flavor enhancers. Such liquid products usually comprise a vegetable oil and can optionally include a quantity of additives for stability, performance, and flavor enhancement. A thin, uniform coating of an oil-based product is desirable in order to provide for non-stick baking characteristics in the pan and to prevent over-application of the flavor enhancers. These products generally have a comparatively high viscosity and these relatively viscous products can also include a substantial amount of solids or particles suspended in them.